1. Field of Invention
The present invention relates to circuits generally and more particularly to simulating circuits with cyclic or periodic behavior.
2. Description of Related Art
With the advances of semiconductor and integrated circuit (IC) design technologies and the increasing demands of the corresponding markets, system-on-chip (SoC) ICs with digital and analog contents on one chip have become an important part of the electronics industry. As a result, SoC designs, productions and shipments have grown significantly each year. In this environment SoC business success requires a first-to-market delivery that depends on successful first-pass designs and short design cycles. Efficient and accurate EDA tools are the keys to the success of SoC design.
There are substantial challenges to efficiently and accurately simulate SoC ICs due to analog content generally and especially the RF (radio frequency) components such as amplifiers, receivers and transceivers where modulated signals are present. The conventional transient analysis is relatively inefficient due to the widely separated spectral components where the high frequency limits the time steps while the low frequency requires long time duration. In some applications, envelope-following simulators have become the basic tools for generating first-pass successful wireless system and RFIC designs [1-3]. The conventional envelope simulation algorithms are modulated-oriented harmonic balance (MOHB) based on harmonic balance technique [4-6] and transient envelope following (TEF) based on shooting Newton methods [7-8]. Both MOHB and TEF require two loops in the envelope simulation and suffer from limited capacity.
There is inherently a tradeoff between speed and accuracy however. In many operational settings envelope following methods cannot achieve the accuracy that can be obtained by the conventional transient analysis. Thus, there is a need for improved methods for simulating circuits with cyclic behavior including circuits with widely separated spectral components.